Electrical conductor paths

ABSTRACT

A component, for example an aerofoil vane or other gas path structure in a gas turbine machine such as a gas turbine engine, in which an insulated electrical conductor path ( 2 ) is embedded structurally integrally, and in which electromagnetic shielding ( 1, 2, 20,   22 ), for the embedded electrical conductor path is provided structurally integrally.

The present invention relates to the provision of electrical conductorpaths.

In conventional instrumentation, for example in a gas turbine engine foraircraft, the power supply or signal to or from a measuring device iscarried electrically along a wire. At least in the case that the wirecarries a high frequency alternating current, the wire must be shieldedto suppress unwanted electromagnetic effects arising from the current.Shielding may also be needed to protect the wire from electromagneticeffects due to currents flowing elsewhere in the engine or otherwise inthe vicinity, for example to avoid falsification of measurement results.

Where the measuring device is located in a relatively inaccessible placein the engine, it may be convenient for the wire carrying the signal tobe routed along or through an aerofoil vane, or other gas path structureof the engine. In this case, conventionally, the wire has either beenpassed through a hole in the structure concerned, or attached to theside of the structure concerned. Such conventional arrangements can giverise to disadvantages.

According to the present invention there is provided a component, forexample an aerofoil vane or other gas path structure in a gas turbinemachine, e.g. a gas turbine engine for instance for aircraft, or a gasturbine generator, in which an insulated electrical conductor path isembedded structurally integrally, and in which electromagnetic shieldingfor the embedded electrical conductor path is provided structurallyintegrally.

The conventional arrangements mentioned above generally involvepost-production modification of a component to provide accommodation fora wire for carrying a signal.

In contrast, in embodiments of the present invention, an electricalconductor path is embedded structurally integrally into the componentconcerned in the course of production of the component, thus forming anintrinsic feature of the component. This enables embodiments of theinvention to avoid problems associated with conventional arrangements,to maintain structural integrity of the component concerned, which isparticularly important when the component is an aerofoil vane or othergas path structure in a gas turbine machine, and to provide othersignificant advantages. In embodiments of the invention the embeddedelectrical conductor path may be used to carry a signal or to carrypower. Of course, respective embedded electrical conductor paths may beprovided, in a component concerned, for carrying signal(s) and power.For example, turbomachinery applications of embodiments of the inventioncould include the transmission of driving electrical power, via anembedded electrical conductor path, across a stator vane span to thestator assembly of a radio telemetry transformer. Preferably, the powerfeed is at radio frequencies so that transformer operation isindependent of rotational speed. Disturbances to this power transmissionarising from electromagnetic interference could generate unwanted signalnoise. Similarly it is desirable to minimise electromagneticinterference arising in other neighbouring circuits as a result of thepower transmission. The electromagnetic shielding provided in accordancewith the invention can avoid or minimise such electromagneticinterference problems. A further example of transmission of powerthrough embedded structural conductor paths as provided in accordancewith the invention is the supply of current to strain gauge bridgesprovided on turbomachinery components.

Embodiments of the present invention avoid problems associated with aconventional post-production provision of wiring, e.g. possibledistortion of accuracy of a signal carried by the wire, for example froma measuring device, or electromagnetic effects due to currents flowingelsewhere, and inconvenient increase in the cross-sectional arearequirement in order to accommodate shielding for the wire.

There is also avoided the problem arising with a conventionalarrangement in which a hole has to be provided post-production in thecomponent for the wire, in that if a possibly suitable hole is notincidentally already present in the structure concerned (rarely thecase), the hole has to be specifically machined, which costs time andmoney for the machining and could affect the component in terms ofstructural integrity—the larger the hole needed the greater the possibleimpact on integrity—and therefore introduce a need for additionalengineering analysis time.

There is also avoided the problem arising with a conventionalarrangement in which the wire is attached to the outside of thestructure, rather than passed through a hole, in that it must then beprotected from the gas path (gas flow, temperature, etc) and theobstruction that it causes the gas path must be taken into account.

In embodiments of the invention, in cases in which the conductor path isembedded in a component, such as an aerofoil vane, primarily of anelectrically conductive material, then the electromagnetic shielding maybe inherently provided by that material.

Provision of further shielding would not be required.

In embodiments of the invention, if the component, such as an aerofoilvane for a gas turbine machine, is made of a non-conducting(electrically insulating) fibre reinforced plastic material, selectednon-conducting fibres may be substituted by electrically conductingfibres or filaments such as threads or wires, which can then be used asthe electrical conductor path to carry a signal or power or to providethe function of electromagnetic shielding. This technique of embeddingthe electrical conductor path by integrally weaving the electricalconductor path into the structure of the insulating fibre reinforcedplastic material can ensure high structural integrity of the componentconcerned.

In other embodiments of the invention, where the component is made of anon-conducting fibre or fibre-resin matrix, some fibres may be coated(sized) with a conductive coating. Alternatively thin foil conductorsmay be included with the fibre tows or used to wrap the fibre tows. Thecoated or wrapped fibre tows can then be used as the electricalconductor path to carry a signal or power or to provide the function aselectromagnetic shielding. Again, this technique of embedding theelectrical conductor path effectively by integrally weaving theelectrical conductor path (e.g. coated or wrapped on insulating fibres)into the structure of the insulating fibre reinforced plastic materialcan again ensure high structural integrity of the component concerned.

In further embodiments of the invention, if the structure is made of anon-conducting fibre reinforced plastic material, then one or more pliescould be laid up in such a way that a channel is left into which one ormore electrically conducting filaments threads or wires are placed,which could then be used as electrical conductor path to carry a signalor power or to function as electromagnetic shielding. The threads orwires would then become embedded into the matrix material of the fibrereinforced plastic material and an integral part of the structure. Therecan again be ensured high structural integrity of the componentconcerned.

In further embodiments of the invention, if a component precursorstructure is made of a fibre reinforced plastic material, then one ormore plies could be laid up in such a way that a channel is left, intowhich one or more hollow tubes or other passageway defining members maybe placed, into which one or more wires or shielded wires may beinserted at the conclusion of manufacture or after manufacture. Thehollow tube or other passageway defining member then becomes embeddedinto the matrix material and becomes an integral part of the structure.A suitable choice of tube material would mean that the impact on thestructural integrity of the structure would be minimised. Furthermore,it would for example be possible to manufacture each aerofoil vane in aset—or each vane precursor—in the same way, and only use the tube tocarry a wire for that or those vanes where this is needed.

In other embodiments of the invention, if the component is made of afibre reinforced plastic material, but has a total or partial coveringof metallic erosion protection, this metallic protection could be usedas the electromagnetic shielding. The metallic erosion protection isthen to be electrically insulated from the signal carrying (or powercarrying) electrical conductor path (e.g. wire) by the non-conductingstructural material. The shielding may also be provided by a metallic orconductive coating or paint, the main purpose of which is for erosionprotection, or other surface treatment, or appearance.

In further embodiments of the invention, if the structure is made of afibre reinforced plastic material, wherein the fibres have someelectrical conductivity (for example carbon fibres), then thisconductivity may be sufficient to provide the needs of shielding. Theelectrical insulation is provided by interposing a ply (or plies) orcoating of non-conducting material between the shielding ply (or plies)and the signal or power conductor.

In further embodiments of the invention, if the structure is made of afibre reinforced plastic material, wherein the fibres have someelectrical conductivity (for example carbon fibres), then thisconductivity may be sufficient to carry a signal or power. Theelectrical insulation is provided by interposing a ply (or plies) orcoating of non-conducting (electrically insulating) material between theshielding ply (or plies) and the signal or powercarrying conductor.

In other embodiments of the invention, if the structure is made of afibre reinforced plastic material, wherein the fibres have insufficientelectrical conductivity to perform as a shielding, and there is nometallic erosion protection, or the metallic erosion protection is onlypartial, then full shielding could be obtained by including a thin plyof metal foil or mesh in the lay-up of the fibre reinforced plasticmaterial.

Reference is made by way of example to the accompanying drawings, inwhich:

FIG. 1 shows a schematic cross section of a component having anelectrically conducting structure;

FIG. 2 shows a schematic view of part of a fibre ply of a componenthaving a fibre reinforced plastic material structure;

FIG. 3 shows a schematic cross section of a component having anelectrically insulating structure;

FIG. 4 shows a schematic cross section of a component havingelectrically conducting and electrically insulating structure; and

FIG. 5 schematically illustrates, in an exploded view, an arrangement ofplies for a component having a fibre reinforced plastic materialstructure.

FIG. 1 illustrates a component in accordance with an embodiment of theinvention, in this case an aerofoil vane of a gas turbine engine, havingan electrically conducting, e.g. metal, structure 1 within which thereis embedded structurally integrally an electrical conductor path 2, forexample a wire, with a structurally integrally embedded electricalinsulator 3, insulating the conductor path 2 from the conductingstructure 1. The electrical conductor path 2 is embedded structurallyintegrally into the structure in the course of production of thecomponent, as is the electrical insulator 3, thus forming intrinsicfeatures of the component as manufactured. In this embodiment theconducting structure 1 itself provides for electromagnetic shielding ofthe conductor path 2. The conductor path 2 may thus safely carry asignal, for example from a measuring device or sensor, or carry power,without further shielding measures.

FIG. 2 shows a schematic view of part of a fibre ply of a componentembodying the present invention having a fibre reinforced plasticmaterial structure. Typically, in such a structure, a number of plies,each a weave of fibres, are laid up in appropriate manner and bondedtogether to an integral structure with a plastic matrix material orresin. In the case illustrated in FIG. 2 the fibres 10 arenon-conducting (electrically insulating) fibre. However one or morefibres are substituted by electrically conducting fibres or filaments 2,for example wires, which can then be used as the electrical conductorpath to carry a signal or power or to provide the function aselectromagnetic shielding. This technique of embedding the electricalconductor path by integrally weaving into the structure of theinsulating fibre reinforced plastic material in the course of productionof the component can ensure high structural integrity of the componentconcerned.

FIG. 3 shows a schematic cross section of a component in accordance withthe invention, in this case an aerofoil vane of a gas turbine engine,having an electrically insulating structure 1A, for example of a fibrereinforced plastic material. The aerofoil vane is provided in this casewith a metallic erosion resistant coating or strip 20, at least at avane edge which is likely to be subject to erosion in operation of theengine, as is shown in the Figure. Of course the vane may be providedwith a more extensive or total covering of metallic erosion protection.In the embodiment, by suitable positioning of the electrical conductorpath 2, embedded structurally integrally in the insulator structure 1Ain the course of production of the component, to be screened at least inpart by the metallic erosion resistant coating or strip 20, thismetallic protection can also provide the electromagnetic shielding forthe conductor path 2, so that no additional measures are needed. Themetallic erosion protection 20 is electrically insulated from the signalor power carrying wire by the non-conducting structural material 1A. Theshielding 20 may also be provided by a metallic or conductive coating orpaint, the main purpose of which may be for erosion protection, but mayotherwise be for surface treatment, or for appearance.

FIG. 4 shows a schematic cross section of a component in accordance withthe invention, in this case an aerofoil vane of a gas turbine engine,having electrically conducting and electrically insulating structure. Inthis embodiment the structure comprises an electrically conducting core2 of a fibre reinforced plastic material wherein the fibres have someelectrical conductivity (for example carbon fibres), which is sufficientto provide an electrical conductor path for carrying a signal and insome cases for carrying power. The core 2 is surrounded by a ply orplies or coating of non-conducting (electrically insulating) material 3.In turn the non-conducting material 3 is surrounded by electricallyconducting ply or plies of a fibre reinforced plastic material 22wherein the fibres have some electrical conductivity (for example carbonfibres), which is sufficient to provide an electromagnetic shieldingfunction. Thus, the insulator 3 is interposed between the shielding ply(plies) 22 and the signal-carrying conductor (ply or plies) 2. In theembodiment illustrated in FIG. 4, a metallic erosion resistant coatingor strip 20 is also provided.

FIG. 5 schematically illustrates, in an exploded view, an arrangementfor plies for a component in accordance with the invention, for examplean aerofoil vane of a gas turbine engine, having a fibre reinforcedplastic material structure. In this embodiment the component, or acomponent precursor structure, is made of a fibre reinforced plasticmaterial in which one or more of the plies 100 are laid up in such a waythat there is a gap 102 between plies (seen in the centre of theexploded array of plies in the Figure) which leaves a channel, intowhich one or more hollow tubes or other passageway defining members (notshown) may be placed, into which one or more electrical conductor paths2, for example wires or shielded wires, may be inserted at conclusion ofmanufacture or after manufacture of the component is completed. Thehollow tube or tubes then become embedded into the matrix material fibrereinforced plastic material structure and becomes an integral part ofthe structure. A suitable choice of tube material can ensure thatstructural integrity of the structure is not tangibly affected.

Furthermore, in this way it is possible for example to manufacture eachaerofoil vane in a set in the same way, i.e. each with a channel or tubefor an electrical conductor path, and only use the tube to carry anelectrical conductor path, e.g. wire, for that or those vanes where thisis needed.

Thus it will be appreciated that embodiments of the present inventionprovide for embedded electrical conductor paths integral to thecomponent concerned, for example an aerofoil vane or other gas pathstructure of a gas turbine machine such as a gas turbine engine, forinstance for connection of instrumentation, in such a manner the gaspath distortion is avoided. The electrical conductor paths areintegrated and form an embedded or intrinsic part of the component andcontribute to, or do not significantly adversely affect, the strength ofthe component. The integral structure of components in accordance withembodiments of the invention supports the electrical conductor paths sopermitting smaller conductive cables, wires or threads to be used, whichreduces is parasitic weight.

Some embodiments of the invention permit production parts, i.e.component precursors, to be instrument ready should the need arise.

Conductive fibres providing conductive paths in some embodiments of theinventions may be of the same nature as the structural fibres (eg carbonfilaments) used in the composite component concerned, in which caseinsulation may be achieved by coating individual fibres with anon-conducting material. Alternatively, in a non-conducting matrix withnon-conducting reinforcement, conductivity of reinforcement fibres mightbe achieved by coating with a conductive material.

Although embodiments of the present invention as described aboveprimarily relate to turbomachinery such as gas turbine engines, someembodiments of the invention may find application in other fields.

For example, the layout of components in modern electronic devices (e.g.computers, televisions, washing machines etc) has to be specificallydesigned from the point of view of electromagnetic shielding. This isparticularly an issue in very compact electronics, where space is aprime concern (for example on a mother-board for a mobile phone, PDA, oreven within a chip). Fibre reinforced plastics provide a strong,lightweight solution for casings for such objects, and potential for thecasing to form a part of an electrical circuit in similar manner asoutlined in embodiments described above in connection with gas turbineengines. There is even potential to embed active electronic componentswithin the lay-up of plies of the fibre reinforced plastics, at least solong as the plastic matrix material cure temperature is below themaximum for the electronic components.

1. A component in which an insulated electrical conductor path isembedded structurally integrally, and in which electromagnetic shieldingfor the embedded electrical conductor path is provided structurallyintegrally.
 2. A component as claimed in claim 1, being a gas pathstructure of a gas turbine machine.
 3. A component as claimed in claim2, being an aerofoil vane of a gas turbine machine.
 4. A component asclaimed in claim 1, having a fibre reinforced plastic structurecomprising plies each a weave of fibres and a matrix material in whichthe plies are embedded.
 5. A component as claimed in claim 4, whereinplies of the fibre reinforced plastic structure comprise each a weave ofelectrically insulating fibres, and wherein an electrically insulatingfibre is substituted by an electrically conducting fibre integrallywoven into the ply concerned, the electrically conducting fibre therebyproviding the electrical conductor path or the electromagneticshielding.
 6. A component as claimed in claim 4, wherein plies of thefibre reinforced plastic structure comprise each a weave of electricallyinsulating fibres, and wherein an electrically insulating fibre isprovided with an electrically conducting covering integrally woven withthe fibre into the ply concerned, the fiber having the electricallyconducting covering thereby providing the electrical conductor path orthe electromagnetic shielding.
 7. A component as claimed in claim 4,wherein one or more plies, comprising each a weave of electricallyinsulating fibres, are laid up in such a way that a channel is providedin which one or more electrically conducting members are embedded,thereby providing the electrical conductor path and/or theelectromagnetic shielding.
 8. A component as claimed in claim 4, whereinat least some of the plies are of fibres having some electricalconductivity, such that they provide the electrical conductor pathand/or the electromagnetic shielding.
 9. A component as claimed in claim8, wherein plies of fibres having some electrical conductivity providethe electrical conductor path and the electromagnetic shielding, theplies of the electrical conductor path and the plies of theelectromagnetic shielding being electrically insulated from one another.10. A component as claimed in claim 9, wherein the plies of theelectrical conductor path and the plies of the electromagnetic shieldingare electrically insulated from one another by a ply or plies ofelectrically insulating fibres.
 11. A component as claimed in claim 1,comprising a conductive surface coating which provides electromagneticshielding.
 12. A component as claimed in claim 11, the component being agas path structure of a gas turbine machine, wherein the conductivesurface coating is an erosion protection coating on the gas pathstructure.
 13. A precursor of a component as claimed in claim 1, havinga fibre reinforced plastic structure comprising plies, each a weave offibres, and a matrix material in which the plies are embedded, whereinone or more plies, comprising each a weave of electrically insulatingfibres, are laid up in such a way that a channel is provided in whichthere is embedded one or more passageway defining members, providingpassageways in the completed precursor, into which passageways one ormore electrically conducting members may be subsequently by introducedto provide the electrical conductor path and/or the electromagneticshielding.
 14. A gas turbine machine comprising a component as claimedin claim 1.